To prevent accidental start-up of fluid operated tools such as grinders, nutsetters, buffers and similar tools having fluid motors, efforts have been directed to prevent accidental throttle lever actuation which in turn serves to operate a valve controlling fluid flow to effect motor start-up. This is particularly important in tools having a generally tubular body connected to a source of pneumatic pressure, e.g., through an attached pressurized air hose wherein the hose itself may whip and roll an unattended tool and accidentally effect tool start-up.
Conventional approaches to date have sought to prevent accidental tool start-up by locking the throttle lever. Various types of safety throttle release devices have been proposed which first must be operated to release the initially locked throttle lever to permit tool operation.
Such known devices normally are subject to abuse and, in the event of undue force being applied when the throttle lever is locked against movement, parts damage may occur. Moreover, the known devices conventionally have an externally located throttle valve lock which is subject to being tampered with or being removed in its entirety, thereby defeating the safety purpose of such devices.
It is accordingly an object of this invention to provide a safety device of the type described which is tamper resistant and contained within an overall tool envelope of minimized size to permit maximum flexibility in the tool application and which features a freely movable throttle valve control requiring a purposeful two-step operating action to effect tool start-up while minimizing any possibility of inadvertent or accidental working of the tool which may cause accidental damage or injury upon unintended full throttle actuation of the tool.